The long term interest of this laboratory lies in understanding the control of gene activity. In depth studies of bacteria and their viruses have long revealed the importance of specific interactions between segments of the chromosome and controlling proteins in governing whether a given gene is expressed. For some time we have develop our efforts to studying the mechanism of gene regulation in the L-arabinose system E. coli. This system has provided us with the first example of positive gene control, and the genetic and biochemical analyses that followed have revealed an intricate pattern of regulation, involving both positive and negative mechanisms. Advances in molecular techniques in gene manipulations, combined with our familiarity with this system, have brought considerable insight into the biochemical events that govern gene activity. The proposed research addresses the molecular interactions between regulatory proteins and DNA, and the mechanisms involved in transcriptional activation. We have utilized methodologies whereby specific regulatory proteins may be added to purified target sites in vitro, and their interactions monitored by a variety of physical, biochemical, and biologic methods. We plan to pursue the study of the mechanism of transcriptional activation at the ara operon promoter by the regulatory proteins AraC and CAP, to compare their modes of action and to test their interdependence. We will also carry out genetic and biochemical dissections of the regulatory protein AraC and its target sites on the DNA. Our goal is to arrive at a better understanding of the molecular mechanisms involved.